feat: add hex

src/hex.cpp

@@ -0,0 +1,38 @@
+#include <cpputils/hex.h>
+#include <iomanip>
+#include <ios>
+#include <string>
+
+namespace cpputils {
+namespace hex {
+
+std::string toHex(std::string const& input) {
+  std::stringstream ss;
+  for (auto c : input) {
+    ss << std::hex << std::setw(2) << std::setfill('0')
+       << static_cast<unsigned int>(static_cast<unsigned char>(c));
+  }
+  return ss.str();
+}
+
+std::string fromHex(std::string const& input) {
+  if (input.size() % 2 != 0) {
+    return {};
+  }
+  std::string out;
+  out.reserve(input.size() / 2);
+
+  for (size_t i = 0; i < input.size(); i += 2) {
+    int hi = hexVal(input[i]);
+    int lo = hexVal(input[i + 1]);
+    if (hi < 0 || lo < 0) {
+      return {};
+    }
+
+    out.push_back(static_cast<char>((hi << 4) | lo));
+  }
+  return out;
+}
+
+}  // namespace hex
+}  // namespace cpputils